/*-
 * Copyright (c) 2014 Andrew Turner
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */

#include "opt_ddb.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/asan.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/msan.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/ptrace.h>
#include <sys/syscall.h>
#include <sys/sysent.h>
#ifdef KDB
#include <sys/kdb.h>
#endif

#include <vm/vm.h>
#include <vm/pmap.h>
#include <vm/vm_kern.h>
#include <vm/vm_map.h>
#include <vm/vm_param.h>
#include <vm/vm_extern.h>

#include <machine/frame.h>
#include <machine/md_var.h>
#include <machine/pcb.h>
#include <machine/pcpu.h>
#include <machine/undefined.h>

#ifdef KDTRACE_HOOKS
#include <sys/dtrace_bsd.h>
#endif

#ifdef VFP
#include <machine/vfp.h>
#endif

#ifdef KDB
#include <machine/db_machdep.h>
#endif

#ifdef DDB
#include <ddb/ddb.h>
#include <ddb/db_sym.h>
#endif

/* Called from exception.S */
void do_el1h_sync(struct thread *, struct trapframe *);
void do_el0_sync(struct thread *, struct trapframe *);
void do_el0_error(struct trapframe *);
void do_serror(struct trapframe *);
void unhandled_exception(struct trapframe *);

static void print_gp_register(const char *name, uint64_t value);
static void print_registers(struct trapframe *frame);

int (*dtrace_invop_jump_addr)(struct trapframe *);

u_long cnt_efirt_faults;
int print_efirt_faults;

typedef void (abort_handler)(struct thread *, struct trapframe *, uint64_t,
    uint64_t, int);

static abort_handler align_abort;
static abort_handler data_abort;
static abort_handler external_abort;

static abort_handler *abort_handlers[] = {
	[ISS_DATA_DFSC_TF_L0] = data_abort,
	[ISS_DATA_DFSC_TF_L1] = data_abort,
	[ISS_DATA_DFSC_TF_L2] = data_abort,
	[ISS_DATA_DFSC_TF_L3] = data_abort,
	[ISS_DATA_DFSC_AFF_L1] = data_abort,
	[ISS_DATA_DFSC_AFF_L2] = data_abort,
	[ISS_DATA_DFSC_AFF_L3] = data_abort,
	[ISS_DATA_DFSC_PF_L1] = data_abort,
	[ISS_DATA_DFSC_PF_L2] = data_abort,
	[ISS_DATA_DFSC_PF_L3] = data_abort,
	[ISS_DATA_DFSC_ALIGN] = align_abort,
	[ISS_DATA_DFSC_EXT] =  external_abort,
	[ISS_DATA_DFSC_EXT_L0] =  external_abort,
	[ISS_DATA_DFSC_EXT_L1] =  external_abort,
	[ISS_DATA_DFSC_EXT_L2] =  external_abort,
	[ISS_DATA_DFSC_EXT_L3] =  external_abort,
	[ISS_DATA_DFSC_ECC] =  external_abort,
	[ISS_DATA_DFSC_ECC_L0] =  external_abort,
	[ISS_DATA_DFSC_ECC_L1] =  external_abort,
	[ISS_DATA_DFSC_ECC_L2] =  external_abort,
	[ISS_DATA_DFSC_ECC_L3] =  external_abort,
};

static __inline void
call_trapsignal(struct thread *td, int sig, int code, void *addr, int trapno)
{
	ksiginfo_t ksi;

	ksiginfo_init_trap(&ksi);
	ksi.ksi_signo = sig;
	ksi.ksi_code = code;
	ksi.ksi_addr = addr;
	ksi.ksi_trapno = trapno;
	trapsignal(td, &ksi);
}

int
cpu_fetch_syscall_args(struct thread *td)
{
	struct proc *p;
	syscallarg_t *ap, *dst_ap;
	struct syscall_args *sa;

	p = td->td_proc;
	sa = &td->td_sa;
	ap = td->td_frame->tf_x;
	dst_ap = &sa->args[0];

	sa->code = td->td_frame->tf_x[8];
	sa->original_code = sa->code;

	if (__predict_false(sa->code == SYS_syscall || sa->code == SYS___syscall)) {
		sa->code = *ap++;
	} else {
		*dst_ap++ = *ap++;
	}

	if (__predict_false(sa->code >= p->p_sysent->sv_size))
		sa->callp = &nosys_sysent;
	else
		sa->callp = &p->p_sysent->sv_table[sa->code];

	KASSERT(sa->callp->sy_narg <= nitems(sa->args),
	    ("Syscall %d takes too many arguments", sa->code));

	memcpy(dst_ap, ap, (nitems(sa->args) - 1) * sizeof(*dst_ap));

	td->td_retval[0] = 0;
	td->td_retval[1] = 0;

	return (0);
}

#include "../../kern/subr_syscall.c"

/*
 * Test for fault generated by given access instruction in
 * bus_peek_<foo> or bus_poke_<foo> bus function.
 */
extern uint32_t generic_bs_peek_1f, generic_bs_peek_2f;
extern uint32_t generic_bs_peek_4f, generic_bs_peek_8f;
extern uint32_t generic_bs_poke_1f, generic_bs_poke_2f;
extern uint32_t generic_bs_poke_4f, generic_bs_poke_8f;

static bool
test_bs_fault(void *addr)
{
	return (addr == &generic_bs_peek_1f ||
	    addr == &generic_bs_peek_2f ||
	    addr == &generic_bs_peek_4f ||
	    addr == &generic_bs_peek_8f ||
	    addr == &generic_bs_poke_1f ||
	    addr == &generic_bs_poke_2f ||
	    addr == &generic_bs_poke_4f ||
	    addr == &generic_bs_poke_8f);
}

static void
svc_handler(struct thread *td, struct trapframe *frame)
{

	if ((frame->tf_esr & ESR_ELx_ISS_MASK) == 0) {
		syscallenter(td);
		syscallret(td);
	} else {
		call_trapsignal(td, SIGILL, ILL_ILLOPN, (void *)frame->tf_elr,
		    ESR_ELx_EXCEPTION(frame->tf_esr));
		userret(td, frame);
	}
}

static void
align_abort(struct thread *td, struct trapframe *frame, uint64_t esr,
    uint64_t far, int lower)
{
	if (!lower) {
		print_registers(frame);
		print_gp_register("far", far);
		printf(" esr: 0x%.16lx\n", esr);
		panic("Misaligned access from kernel space!");
	}

	call_trapsignal(td, SIGBUS, BUS_ADRALN, (void *)frame->tf_elr,
	    ESR_ELx_EXCEPTION(frame->tf_esr));
	userret(td, frame);
}


static void
external_abort(struct thread *td, struct trapframe *frame, uint64_t esr,
    uint64_t far, int lower)
{
	if (lower) {
		call_trapsignal(td, SIGBUS, BUS_OBJERR, (void *)far,
		    ESR_ELx_EXCEPTION(frame->tf_esr));
		userret(td, frame);
		return;
	}

	/*
	 * Try to handle synchronous external aborts caused by
	 * bus_space_peek() and/or bus_space_poke() functions.
	 */
	if (test_bs_fault((void *)frame->tf_elr)) {
		frame->tf_elr = (uint64_t)generic_bs_fault;
		return;
	}

	print_registers(frame);
	print_gp_register("far", far);
	printf(" esr: 0x%.16lx\n", esr);
	panic("Unhandled external data abort");
}

/*
 * It is unsafe to access the stack canary value stored in "td" until
 * kernel map translation faults are handled, see the pmap_klookup() call below.
 * Thus, stack-smashing detection with per-thread canaries must be disabled in
 * this function.
 */
static void NO_PERTHREAD_SSP
data_abort(struct thread *td, struct trapframe *frame, uint64_t esr,
    uint64_t far, int lower)
{
	struct vm_map *map;
	struct pcb *pcb;
	vm_prot_t ftype;
	int error, sig, ucode;
#ifdef KDB
	bool handled;
#endif

	/*
	 * According to the ARMv8-A rev. A.g, B2.10.5 "Load-Exclusive
	 * and Store-Exclusive instruction usage restrictions", state
	 * of the exclusive monitors after data abort exception is unknown.
	 */
	clrex();

#ifdef KDB
	if (kdb_active) {
		kdb_reenter();
		return;
	}
#endif

	if (lower) {
		map = &td->td_proc->p_vmspace->vm_map;
	} else if (!ADDR_IS_CANONICAL(far)) {
		/* We received a TBI/PAC/etc. fault from the kernel */
		error = KERN_INVALID_ADDRESS;
		pcb = td->td_pcb;
		goto bad_far;
	} else if (ADDR_IS_KERNEL(far)) {
		/*
		 * Handle a special case: the data abort was caused by accessing
		 * a thread structure while its mapping was being promoted or
		 * demoted, as a consequence of the break-before-make rule.  It
		 * is not safe to enable interrupts or dereference "td" before
		 * this case is handled.
		 *
		 * In principle, if pmap_klookup() fails, there is no need to
		 * call pmap_fault() below, but avoiding that call is not worth
		 * the effort.
		 */
		if (ESR_ELx_EXCEPTION(esr) == EXCP_DATA_ABORT) {
			switch (esr & ISS_DATA_DFSC_MASK) {
			case ISS_DATA_DFSC_TF_L0:
			case ISS_DATA_DFSC_TF_L1:
			case ISS_DATA_DFSC_TF_L2:
			case ISS_DATA_DFSC_TF_L3:
				if (pmap_klookup(far, NULL))
					return;
				break;
			}
		}
		if (td->td_md.md_spinlock_count == 0 &&
		    (frame->tf_spsr & PSR_DAIF_INTR) != PSR_DAIF_INTR) {
			MPASS((frame->tf_spsr & PSR_DAIF_INTR) == 0);
			intr_enable();
		}
		map = kernel_map;
	} else {
		if (td->td_md.md_spinlock_count == 0 &&
		    (frame->tf_spsr & PSR_DAIF_INTR) != PSR_DAIF_INTR) {
			MPASS((frame->tf_spsr & PSR_DAIF_INTR) == 0);
			intr_enable();
		}
		map = &td->td_proc->p_vmspace->vm_map;
		if (map == NULL)
			map = kernel_map;
	}
	pcb = td->td_pcb;

	/*
	 * Try to handle translation, access flag, and permission faults.
	 * Translation faults may occur as a result of the required
	 * break-before-make sequence used when promoting or demoting
	 * superpages.  Such faults must not occur while holding the pmap lock,
	 * or pmap_fault() will recurse on that lock.
	 */
	if ((lower || map == kernel_map || pcb->pcb_onfault != 0) &&
	    pmap_fault(map->pmap, esr, far) == KERN_SUCCESS)
		return;

#ifdef INVARIANTS
	if (td->td_md.md_spinlock_count != 0) {
		print_registers(frame);
		print_gp_register("far", far);
		printf(" esr: 0x%.16lx\n", esr);
		panic("data abort with spinlock held (spinlock count %d != 0)",
		    td->td_md.md_spinlock_count);
	}
#endif
	if ((td->td_pflags & TDP_NOFAULTING) == 0 &&
	    (td->td_critnest != 0 || WITNESS_CHECK(WARN_SLEEPOK |
	    WARN_GIANTOK, NULL, "Kernel page fault") != 0)) {
		print_registers(frame);
		print_gp_register("far", far);
		printf(" esr: 0x%.16lx\n", esr);
		panic("data abort in critical section or under mutex");
	}

	switch (ESR_ELx_EXCEPTION(esr)) {
	case EXCP_INSN_ABORT:
	case EXCP_INSN_ABORT_L:
		ftype = VM_PROT_EXECUTE;
		break;
	default:
		/*
		 * If the exception was because of a read or cache operation
		 * pass a read fault type into the vm code. Cache operations
		 * need read permission but will set the WnR flag when the
		 * memory is unmapped.
		 */
		if ((esr & ISS_DATA_WnR) == 0 || (esr & ISS_DATA_CM) != 0)
			ftype = VM_PROT_READ;
		else
			ftype = VM_PROT_WRITE;
		break;
	}

	/* Fault in the page. */
	error = vm_fault_trap(map, far, ftype, VM_FAULT_NORMAL, &sig, &ucode);
	if (error != KERN_SUCCESS) {
		if (lower) {
			call_trapsignal(td, sig, ucode, (void *)far,
			    ESR_ELx_EXCEPTION(esr));
		} else {
bad_far:
			if (td->td_intr_nesting_level == 0 &&
			    pcb->pcb_onfault != 0) {
				frame->tf_elr = pcb->pcb_onfault;
				return;
			}

			printf("Fatal data abort:\n");
			print_registers(frame);
			print_gp_register("far", far);
			printf(" esr: 0x%.16lx\n", esr);

#ifdef KDB
			if (debugger_on_trap) {
				kdb_why = KDB_WHY_TRAP;
				handled = kdb_trap(ESR_ELx_EXCEPTION(esr), 0,
				    frame);
				kdb_why = KDB_WHY_UNSET;
				if (handled)
					return;
			}
#endif
			panic("vm_fault failed: 0x%lx error %d",
			    frame->tf_elr, error);
		}
	}

	if (lower)
		userret(td, frame);
}

static void
print_gp_register(const char *name, uint64_t value)
{
#if defined(DDB)
	c_db_sym_t sym;
	const char *sym_name;
	db_expr_t sym_value;
	db_expr_t offset;
#endif

	printf(" %s: 0x%.16lx", name, value);
#if defined(DDB)
	/* If this looks like a kernel address try to find the symbol */
	if (value >= VM_MIN_KERNEL_ADDRESS) {
		sym = db_search_symbol(value, DB_STGY_ANY, &offset);
		if (sym != C_DB_SYM_NULL) {
			db_symbol_values(sym, &sym_name, &sym_value);
			printf(" (%s + 0x%lx)", sym_name, offset);
		}
	}
#endif
	printf("\n");
}

static void
print_registers(struct trapframe *frame)
{
	char name[4];
	u_int reg;

	for (reg = 0; reg < nitems(frame->tf_x); reg++) {
		snprintf(name, sizeof(name), "%sx%d", (reg < 10) ? " " : "",
		    reg);
		print_gp_register(name, frame->tf_x[reg]);
	}
	printf("  sp: 0x%.16lx\n", frame->tf_sp);
	print_gp_register(" lr", frame->tf_lr);
	print_gp_register("elr", frame->tf_elr);
	printf("spsr: 0x%.16lx\n", frame->tf_spsr);
}

#ifdef VFP
static void
fpe_trap(struct thread *td, void *addr, uint32_t exception)
{
	int code;

	code = FPE_FLTIDO;
	if ((exception & ISS_FP_TFV) != 0) {
		if ((exception & ISS_FP_IOF) != 0)
			code = FPE_FLTINV;
		else if ((exception & ISS_FP_DZF) != 0)
			code = FPE_FLTDIV;
		else if ((exception & ISS_FP_OFF) != 0)
			code = FPE_FLTOVF;
		else if ((exception & ISS_FP_UFF) != 0)
			code = FPE_FLTUND;
		else if ((exception & ISS_FP_IXF) != 0)
			code = FPE_FLTRES;
	}
	call_trapsignal(td, SIGFPE, code, addr, exception);
}
#endif

/*
 * See the comment above data_abort().
 */
void NO_PERTHREAD_SSP
do_el1h_sync(struct thread *td, struct trapframe *frame)
{
	uint32_t exception;
	uint64_t esr, far;
	int dfsc;

	kasan_mark(frame, sizeof(*frame), sizeof(*frame), 0);
	kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED);

	far = frame->tf_far;
	/* Read the esr register to get the exception details */
	esr = frame->tf_esr;
	exception = ESR_ELx_EXCEPTION(esr);

#ifdef KDTRACE_HOOKS
	if (dtrace_trap_func != NULL && (*dtrace_trap_func)(frame, exception))
		return;
#endif

	CTR4(KTR_TRAP, "%s: exception=%lu, elr=0x%lx, esr=0x%lx",
	    __func__, exception, frame->tf_elr, esr);

	/*
	 * Enable debug exceptions if we aren't already handling one. They will
	 * be masked again in the exception handler's epilogue.
	 */
	switch (exception) {
	case EXCP_BRK:
	case EXCP_BRKPT_EL1:
	case EXCP_WATCHPT_EL1:
	case EXCP_SOFTSTP_EL1:
		break;
	default:
		dbg_enable();
		break;
	}

	switch (exception) {
	case EXCP_FP_SIMD:
	case EXCP_TRAP_FP:
#ifdef VFP
		if ((td->td_pcb->pcb_fpflags & PCB_FP_KERN) != 0) {
			vfp_restore_state();
		} else
#endif
		{
			print_registers(frame);
			printf(" esr: 0x%.16lx\n", esr);
			panic("VFP exception in the kernel");
		}
		break;
	case EXCP_INSN_ABORT:
	case EXCP_DATA_ABORT:
		dfsc = esr & ISS_DATA_DFSC_MASK;
		if (dfsc < nitems(abort_handlers) &&
		    abort_handlers[dfsc] != NULL) {
			abort_handlers[dfsc](td, frame, esr, far, 0);
		} else {
			print_registers(frame);
			print_gp_register("far", far);
			printf(" esr: 0x%.16lx\n", esr);
			panic("Unhandled EL1 %s abort: 0x%x",
			    exception == EXCP_INSN_ABORT ? "instruction" :
			    "data", dfsc);
		}
		break;
	case EXCP_BRK:
#ifdef KDTRACE_HOOKS
		if ((esr & ESR_ELx_ISS_MASK) == 0x40d /* BRK_IMM16_VAL */ &&
		    dtrace_invop_jump_addr != NULL &&
		    dtrace_invop_jump_addr(frame) == 0)
			break;
#endif
#ifdef KDB
		kdb_trap(exception, 0, frame);
#else
		panic("No debugger in kernel.");
#endif
		break;
	case EXCP_BRKPT_EL1:
	case EXCP_WATCHPT_EL1:
	case EXCP_SOFTSTP_EL1:
#ifdef KDB
		kdb_trap(exception, 0, frame);
#else
		panic("No debugger in kernel.");
#endif
		break;
	case EXCP_FPAC:
		/* We can see this if the authentication on PAC fails */
		print_registers(frame);
		print_gp_register("far", far);
		panic("FPAC kernel exception");
		break;
	case EXCP_UNKNOWN:
		print_registers(frame);
		print_gp_register("far", far);
		panic("Undefined instruction: %08x",
		    *(uint32_t *)frame->tf_elr);
		break;
	case EXCP_BTI:
		print_registers(frame);
		print_gp_register("far", far);
		panic("Branch Target exception");
		break;
	default:
		print_registers(frame);
		print_gp_register("far", far);
		panic("Unknown kernel exception 0x%x esr_el1 0x%lx", exception,
		    esr);
	}
}

void
do_el0_sync(struct thread *td, struct trapframe *frame)
{
	pcpu_bp_harden bp_harden;
	uint32_t exception;
	uint64_t esr, far;
	int dfsc;

	/* Check we have a sane environment when entering from userland */
	KASSERT((uintptr_t)get_pcpu() >= VM_MIN_KERNEL_ADDRESS,
	    ("Invalid pcpu address from userland: %p (tpidr 0x%lx)",
	     get_pcpu(), READ_SPECIALREG(tpidr_el1)));

	kasan_mark(frame, sizeof(*frame), sizeof(*frame), 0);
	kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED);

	far = frame->tf_far;
	esr = frame->tf_esr;
	exception = ESR_ELx_EXCEPTION(esr);
	if (exception == EXCP_INSN_ABORT_L && far > VM_MAXUSER_ADDRESS) {
		/*
		 * Userspace may be trying to train the branch predictor to
		 * attack the kernel. If we are on a CPU affected by this
		 * call the handler to clear the branch predictor state.
		 */
		bp_harden = PCPU_GET(bp_harden);
		if (bp_harden != NULL)
			bp_harden();
	}
	intr_enable();

	CTR4(KTR_TRAP, "%s: exception=%lu, elr=0x%lx, esr=0x%lx",
	    __func__, exception, frame->tf_elr, esr);

	switch (exception) {
	case EXCP_FP_SIMD:
#ifdef VFP
		vfp_restore_state();
#else
		panic("VFP exception in userland");
#endif
		break;
	case EXCP_TRAP_FP:
#ifdef VFP
		fpe_trap(td, (void *)frame->tf_elr, esr);
		userret(td, frame);
#else
		panic("VFP exception in userland");
#endif
		break;
	case EXCP_SVE:
		/* Returns true if this thread can use SVE */
		if (!sve_restore_state(td))
			call_trapsignal(td, SIGILL, ILL_ILLTRP,
			    (void *)frame->tf_elr, exception);
		userret(td, frame);
		break;
	case EXCP_SVC32:
	case EXCP_SVC64:
		svc_handler(td, frame);
		break;
	case EXCP_INSN_ABORT_L:
	case EXCP_DATA_ABORT_L:
	case EXCP_DATA_ABORT:
		dfsc = esr & ISS_DATA_DFSC_MASK;
		if (dfsc < nitems(abort_handlers) &&
		    abort_handlers[dfsc] != NULL)
			abort_handlers[dfsc](td, frame, esr, far, 1);
		else {
			print_registers(frame);
			print_gp_register("far", far);
			printf(" esr: 0x%.16lx\n", esr);
			panic("Unhandled EL0 %s abort: 0x%x",
			    exception == EXCP_INSN_ABORT_L ? "instruction" :
			    "data", dfsc);
		}
		break;
	case EXCP_UNKNOWN:
		if (!undef_insn(frame))
			call_trapsignal(td, SIGILL, ILL_ILLTRP, (void *)far,
			    exception);
		userret(td, frame);
		break;
	case EXCP_FPAC:
		call_trapsignal(td, SIGILL, ILL_ILLOPN, (void *)frame->tf_elr,
		    exception);
		userret(td, frame);
		break;
	case EXCP_SP_ALIGN:
		call_trapsignal(td, SIGBUS, BUS_ADRALN, (void *)frame->tf_sp,
		    exception);
		userret(td, frame);
		break;
	case EXCP_PC_ALIGN:
		call_trapsignal(td, SIGBUS, BUS_ADRALN, (void *)frame->tf_elr,
		    exception);
		userret(td, frame);
		break;
	case EXCP_BRKPT_EL0:
	case EXCP_BRK:
#ifdef COMPAT_FREEBSD32
	case EXCP_BRKPT_32:
#endif /* COMPAT_FREEBSD32 */
		call_trapsignal(td, SIGTRAP, TRAP_BRKPT, (void *)frame->tf_elr,
		    exception);
		userret(td, frame);
		break;
	case EXCP_WATCHPT_EL0:
		call_trapsignal(td, SIGTRAP, TRAP_TRACE, (void *)far,
		    exception);
		userret(td, frame);
		break;
	case EXCP_MSR:
		/*
		 * The CPU can raise EXCP_MSR when userspace executes an mrs
		 * instruction to access a special register userspace doesn't
		 * have access to.
		 */
		if (!undef_insn(frame))
			call_trapsignal(td, SIGILL, ILL_PRVOPC,
			    (void *)frame->tf_elr, exception);
		userret(td, frame);
		break;
	case EXCP_SOFTSTP_EL0:
		PROC_LOCK(td->td_proc);
		if ((td->td_dbgflags & TDB_STEP) != 0) {
			td->td_frame->tf_spsr &= ~PSR_SS;
			td->td_pcb->pcb_flags &= ~PCB_SINGLE_STEP;
			WRITE_SPECIALREG(mdscr_el1,
			    READ_SPECIALREG(mdscr_el1) & ~MDSCR_SS);
		}
		PROC_UNLOCK(td->td_proc);
		call_trapsignal(td, SIGTRAP, TRAP_TRACE,
		    (void *)frame->tf_elr, exception);
		userret(td, frame);
		break;
	case EXCP_BTI:
		call_trapsignal(td, SIGILL, ILL_ILLOPC, (void *)frame->tf_elr,
		    exception);
		userret(td, frame);
		break;
	default:
		call_trapsignal(td, SIGBUS, BUS_OBJERR, (void *)frame->tf_elr,
		    exception);
		userret(td, frame);
		break;
	}

	KASSERT(
	    (td->td_pcb->pcb_fpflags & ~(PCB_FP_USERMASK|PCB_FP_SVEVALID)) == 0,
	    ("Kernel VFP flags set while entering userspace"));
	KASSERT(
	    td->td_pcb->pcb_fpusaved == &td->td_pcb->pcb_fpustate,
	    ("Kernel VFP state in use when entering userspace"));
}

/*
 * TODO: We will need to handle these later when we support ARMv8.2 RAS.
 */
void
do_serror(struct trapframe *frame)
{
	uint64_t esr, far;

	kasan_mark(frame, sizeof(*frame), sizeof(*frame), 0);
	kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED);

	far = frame->tf_far;
	esr = frame->tf_esr;

	print_registers(frame);
	print_gp_register("far", far);
	printf(" esr: 0x%.16lx\n", esr);
	panic("Unhandled System Error");
}

void
unhandled_exception(struct trapframe *frame)
{
	uint64_t esr, far;

	kasan_mark(frame, sizeof(*frame), sizeof(*frame), 0);
	kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED);

	far = frame->tf_far;
	esr = frame->tf_esr;

	print_registers(frame);
	print_gp_register("far", far);
	printf(" esr: 0x%.16lx\n", esr);
	panic("Unhandled exception");
}
